Type I immediate atopic allergies are one of the most common health problems in the Western world, and constantly increasing in prevalence (ISAAC 1998). It has been speculated that this increase is associated with the reduced microbial load in the developed societies, which has weakened natural T regulatory (Treg) and type 1 Th (Th1)-cell responses, giving way to enhanced Th2 responses that characterize atopic diseases.
CD4+ T cells (Treg, Th1 and Th2) are the main regulators of allergic immune response. Th2 cells that secrete cytokines such as IL-4, IL-5 and IL-13 are important to development of allergic inflammation by inducing IgE-production by B cells, degranulation of mast cells and recruitment of eosinophils. The regulatory T cells and their cytokine IL-10 also have an important role in down-regulation of Th2-type responses towards allergens. Th1 cells are essential for defense against microbes, in particular intracellular pathogens, and cancer by inducing activation of cytotoxic T (Tc) cells and natural killer (NK) cells. In addition, Th1-type cytokines, including IFN-γ, IL-12 and IL-18, are involved in suppression of allergen-induced Th2-type immune responses. Moreover, in allergen vaccination, there is up-regulation of the cytokines IFN-γ, IL-10 and IL-18, indicating their crucial role in suppressing the allergic inflammation also in vivo.
Recent research has shown that the crucial time for the development of either Th1- or Th2-type immunity is infancy. At birth, there is a weak Th2-type immunity, which in healthy individuals is conversed to a Th1-type response. It is thought that the priming of the immune system by microbial components in the environment and gut microflora (endotoxins, lactobacilli, mycobacteria) is essential in this conversion.
Research has been performed on the effects of microbial components on Th1-Th2 balance. A great deal of effort has been directed towards the search for microbial molecules, which could be used in development of more effective and safer vaccines for immunization against infections and in novel therapeutic approaches to treat autoimmune, atopic, and malignant diseases. Among these molecules are 3-deacylated monophosphoryl lipid A (MPL), the non-toxic derivative of lipopolysaccharide of Salmonella minnesota (LPS), and immunostimulatory bacterial DNA sequences (CpG-ODN) that generally consist of a central nonmethylated CG di-nucleotide. These molecules have been clinically tested and shown to be effective and well-tolerated adjuvants in a number of vaccines for immunization against and treatment of hepatitis B virus, human immunodeficiency virus (HIV), influenza A virus, and Plasmodium falciparum, as well as in treatment of cancers such as non-Hodgkin lymphoma, and melanoma. These molecules have been shown to function by inducing strong Th1-type pattern of cytokine production by acting on various Toll-like receptors on antigen-presenting cells such as monocytes, macro-phages and dendritic cells. Moreover, the Th1-enhancing effects of mycobacteria and bacterial lipopolysaccharide with subsequent suppression of Th2-type response, allergic inflammation, IgE-responses and bronchial hyperreactivity have been shown in several studies. In addition, probiotic lactobacilli have been shown to reduce the prevalence of atopic eczema at the age of two years when administrated orally during pregnancy and immediately after birth. Immunotherapy with bacterial CpG-ODN oligonucleotides bound covalently to allergens has also been shown to decrease the nasal inflammatory response in allergic rhinitis patients. MPL has been successfully tested as an adjuvant in allergen immune-therapy.
The therapeutic use of these microbial compounds faces certain problems. LPS is a toxin and as such unfit for therapeutic use. CpG-ODN is a gene and, in addition to being expensive for large-scale synthesis, implies potential problems with the public opinion (such as gene manipulated food products). MPL adjuvant is not a single chemical entity, but a mixture of analogues, with differences reflected in the number and length of fatty acid chains. Probiotic lactobacilli are live bacteria, comprising safety problems with respect to possible infections, and furthermore are difficult to standardize. Also mycobacterial lysates are crude mixtures of bacterial components out of range of biological standardization. An ideal therapeutic component for allergy treatment would be a naturally occurring, non-toxic, safe purified molecule with as small molecular size as possible.
In WO 02/09728 complex carbohydrates are presented for prevention and treatment of a variety of over 80 diseases. In this publication carbohydrates are defined as any polymer comprising more than two sugar moieties and including such classes of compounds as polysaccharides (that include mucopoly-saccharides and mannans) and oligosaccharides [that are comprised of branched oligosaccharides such as sialylated sugars including milk sugars; the key milk sugars (also called hexaoses) incorporated in the general class of complex carbohydrates being difucosyllacto-N-hexaose a and b, disialyl-monofucosyllacto-N-hexaose and monofucosyllacto-N-hexaose I, II and II]. The diseases listed include conditions associated with allergies; individually mentioned are anaphylaxis, asthma and itching associated with allergies and hypersensitivity and are based on e.g. inhibition of white cell adhesion.
US 2002/0054886 discloses a vaccine, comprising β-1,2-linked straight chain oligo-mannosyl residues for the treatment of candidiasis. The oligo-mannosyl residues are used as an epitope to elicit a protective antibody response against candidiasis or to prevent Candida albicans adhesion to mammalian cells. The effect is based on the use of a synthetic substance mimicking microbial compounds, administrated to induce a specific immune response against the substance.
WO2006/096970 A1 discloses another application for the treatment of candidiasis. Therein are provided conjugates comprising native O-linked and S-linked oligosaccharides, more specifically β-1,2-linked straight chain oligo-mannosyl residues, coupled to a protein carrier via a linker. Said conjugate always comprises a protein. It is essential that said protein carrier elicits a thymus dependent immune response. The synthesis strategy for linking said moieties is presented as well. The conjugate formed of oligosaccharides and protein carrier covalently attached by a linker, is suggested to be usable for inducing an immune response to a Candida species in a subject in need thereof.
WO2007/010084 discloses immunostimulatory mannan polysaccharides comprising β-1,2-linked chains and β-1,2-(D)-mannooligosaccharides, and their uses for modulating T helper (Th) cell-mediated immune responses. However, the activity of synthesized simple β-1,2-linked mannooligosaccharide chains consisting of up to four oligosaccharides was inferior as compared to natural crude oligosaccharide mixtures. Therefore, novel modifications of these synthetic oligosaccharide chains were needed.